A lady walks into the drugstore and asks the pharmacist for some arsenic.

"Ma'am, what do you want with arsenic?"

"To kill my husband."

"I can't sell you arsenic to kill a person!"

The lady lays down a photo of a man and a woman in a compromising position. The man is her husband and the woman is the pharmacist's wife. He takes the photo and slowly nods.

"I didn't realize you had a prescription."